Valves are commonly used in process fluid handling systems and fluid delivery systems to manipulate the flow of a fluid. In general, a valve may regulate flow by selectively allowing or inhibiting fluid to reach a destination. The fluid pressures associated with the systems often affect the operation of the valves. For example, valves may be opened or closed to manipulate the pressure at different points or stages of a process. In other examples, the operation of a valve may depend on pressure values at defined points in the system.
One example is an internal valve that opens or closes based on a pressure and/or fluid flow rate of the system in which the internal valve is installed. Valves may be installed internally to reduce the possibility of mechanical damage resulting from external sources (e.g., accidental impact, fire, wear, etc.). However, internal valves are less accessible after installation. As a result, in some cases, the valve position or status (e.g., whether the valve is open, closed, in a bleed mode, etc.) is not always clear to an operator.
Where the position of a valve is not available or clear, an operator may be forced to employ manual methods (e.g., operator intervention or involvement may be required) to operate the control system in which the valve is installed. As a result, operator error may be introduced into the control system. For example, the internal valves noted above may employ a flow control mechanism to shut the valve in response to a sudden excess flow condition due to, for example, a broken, severed, or otherwise compromised flow path. Such flow control mechanisms are commonly referred to as excess flow valves, which are often used in applications requiring an automatic, safe cutoff of fluid flow in response to potential leaks, spills, etc. of potentially dangerous (e.g., combustible, toxic) fluids.
When operating a system employing an internal valve having an integral excess flow valve, it is typically necessary to equalize the pressure between the valve inlet and outlet before fluid is pumped through the valve. Without knowledge of the position or operational state of the internal valve (i.e., whether the pressure is equalized) the operator may, for example, prematurely begin to pump fluid based on an estimation of whether the valve is prepared to convey fluid. Such an approach may be inefficient if, for example, several attempted equalizations are performed due to operator error.